There are no related patent applications.
(1) Field of the Invention
The present invention relates generally to acoustic arrays, and more particularly to a fiber optic acoustic array towed from a torpedo and connected to the launching platform for the torpedo.
(2) Description of the Prior Art
During hostile encounters, a submarine has to establish a target""s bearing, and range in the shortest time frame possible. To do so, the submarine will typically let out an acoustic array along a length of tow cable to obtain the acoustic signature of the target. Current improvement efforts for such towed arrays seek to replace the electromechanical hydrophones and cable of these arrays with fiber optical acoustic sensors and cable.
Once the towed array is deployed, the submarine maneuvers in a zigzag pattern in order to obtain sufficient bearing and range information for target acquisition. However, depending on the signal to noise ratio of an acquired signal, target acquisition in this manner may take a considerable mount of time, sometimes on the order of hours. During this time, the submarine is vulnerable to attack by the target or other hostile platform.
Once the target is acquired, a torpedo may be launched from the submarine toward the target. Modern torpedoes are wire-guided and use copper wire for two-way communication between the submarine and the torpedo. Using its onboard and towed array sensors, the submarine continues to obtain and process acoustic signals from the engagement arena. The submarine then provides guidance commands to the torpedo through the copper wire. Typically, the engagement arena will contain numerous countermeasures deployed at the target to thwart the torpedo""s attainment of the target. In this noisy environment, complicated by the submarine""s physical separation from the engagement arena, the submarine""s sensors may not provide sufficient data to separate countermeasure noise from target signatures. Thus, guidance of the torpedo may be inadequate for the torpedo to successfully acquire the target.
Thus, it can be seen that the sooner a torpedo may be launched at a potential target, the greater the margin of safety for the submarine. Also, sensors deployed within the engagement arena will improve signal acquisition, signal processing and torpedo guidance such that the torpedo can successfully engage the target.
Accordingly, it is an object of the present invention to provide a system to obtain acoustic bearing and range data from within an engagement arena for a target in the arena.
Another object of the present invention is to provide a system for target acquisition that provides for early launch of torpedo towards the target.
Still another object of the present invention is to provide a system for guiding a torpedo to a target based on target bearing and range data obtained within the engagement arena.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a system is provided in which a torpedo is launched from a submarine towards a target based on minimal target bearing and range data obtained from a submarine""s onboard or towed acoustic sensors. The target and range data necessary for torpedo launch need only be rough approximations of the target""s position based on data from a few sensors. The torpedo is of the well-known wire-guided type, with the prior art copper wire and related receiving/transmitting equipment being replaced with a monofilament optical fiber and fiber optic receivers/transmitters. In addition to carrying communications between the submarine and torpedo, the optical fiber includes optical acoustic sensors. Thus, as the optical fiber pays out behind the torpedo, an acoustic array is formed. Because the optical fiber pays out at the same rate that the torpedo moves away from the submarine, the optical fiber does not move in relation to the surrounding medium. Thus the flow noises experienced in conventional towed arrays are virtually eliminated from the array of optical acoustic sensors.
The optical fiber serves as a forward deployed acoustic array to gather target bearing and range data that is processed at the submarine. With the array deployed directly within the engagement arena, the submarine can more accurately analyze the acoustic environment to better guide the torpedo through countermeasure avoidance and to target acquisition. With improved inertial guidance and motion tracking, the torpedo may also be guided through a zigzag pattern, or dogleg, to further enhance target and countermeasure bearing data.